Multiple axis robotic additive manufacturing system and methods

ABSTRACT

A multiple axis robotic additive manufacturing system includes a robotic arm movable in six degrees of freedom. The system includes a build platform movable in at least two degrees of freedom and independent of the movement of the robotic arm to position the part being built to counteract effects of gravity based upon part geometry. The system includes an extruder mounted at an end of the robotic arm. The extruder is configured to extrude at least part material with a plurality of flow rates, wherein movement of the robotic arm and the build platform are synchronized with the flow rate of the extruded material to build the 3D part.

BACKGROUND

The present disclosure relates generally to additive manufacturing, andmore specifically to a multiple axis robotic build system.

Additive manufacturing, or 3D printing, is generally an additivemanufacturing process in which a three-dimensional (3D) object is builtutilizing a computer model of the objects. The typical operationconsists of slicing a three-dimensional computer model into thin crosssections, translating the result into two-dimensional position data, andfeeding the data to control a printer which manufactures athree-dimensional structure in a layerwise manner using one or moreadditive manufacturing techniques. Additive manufacturing entails manydifferent approaches to the method of fabrication, including fuseddeposition modeling, ink jetting, selective laser sintering,powder/binder jetting, electron-beam melting, electrophotographicimaging, and stereolithographic processes.

Additive manufacturing technologies can be used for prototyping (whereit has been used for many years) and also for end-use production parts.For end-use part production, it is desirable to print net-shape parts,or near-net shape parts (i.e., parts that match very closely to thedigital image provided as a source data file, and therefore requirelittle or no post-print processing to achieve the desired tolerances forthe size and shape for the part).

In a fused deposition modeling system, a 3D printer creates a 3D printedpart in a layer-by-layer manner by extruding a flowable part materialalong tool paths that are generated from a digital representation of thepart. The part material is extruded through an extrusion tip carried bya print head of the system. The extruded part material fuses topreviously deposited part material, and solidifies upon a drop intemperature. In a typical printer, the material is deposited in planarlayers as a sequence of roads built up on a substrate that defines abuild plane. The position of the print head relative to the substrate isthen incremented along a print axis (perpendicular to the build plane),and the process is then repeated to form a printed part resembling thedigital representation.

In fabricating printed parts by depositing layers of a part material,supporting layers or structures are typically built underneathoverhanging portions or in cavities of printed parts under construction,which are not supported by the part material itself. A support structuremay be built utilizing the same deposition techniques by which the partmaterial is deposited. A host computer generates additional geometryacting as a support structure for the overhanging or free-space segmentsof the printed part being formed. Support material is then depositedpursuant to the generated geometry during the printing process. Thesupport material can adhere to the part material during fabrication, andis removable from the completed printed part when the printing processis complete.

The use of layer-by-layer printing with optional support structure canresult in parts that require long build times, extra post-processing,and require large amounts of support material. Further, parts built withlayer-by-layer printing are limited in the geometries that may beprinted while still providing parts of sufficient quality and strengthfor use in at least some industries.

SUMMARY

One aspect of the present disclosure includes a multiple axis roboticadditive manufacturing system includes a robotic arm movable in sixdegrees of freedom. The system includes a build platform movable in atleast two degrees of freedom and independent of the movement of therobotic arm to position the part being built to counteract effects ofgravity based upon part geometry. The system includes an extrudermounted at an end of the robotic arm. The extruder is configured toextrude at least part material with a plurality of flow rates, whereinmovement of the robotic arm and the build platform are synchronized withthe flow rate of the extruded material to build the 3D part.

Another aspect of the present disclosure relates to a method of printinga 3D part with a multiple axis robotic build system. The method includesprinting at least a portion of the part on a build platform along a 3Dtool path with an extruder mounted on a robotic arm that moves in sixdegrees of freedom. The method further includes orienting the part bymoving the build platform during printing based on a geometry of thepart being printed separate from the movement of the robotic arm whereinthe movement of the build platform and the movement of the robotic armare synchronized to print the part without support structures.

Another aspect of the present disclosure relates to a method printing a3D part in an out of oven printing environment. The method includesproviding an extruder on a robotic arm having six degrees of freedom andproviding a build platform movable in at least two axes of rotation. Themethod includes extruding at least a first segment of a first portion ofthe part along a first 3D tool path and extruding at least a secondsegment of a second portion of the part conformally to a surface of thefirst portion of the part along a second 3D tool path. Extruding asecond portion of the part comprises locally pre-heating a portion ofthe first portion along the second 3D tool path of the second portion ofthe part prior to extruding on that portion of the tool path.

DEFINITIONS

Unless otherwise specified, the following terms as used herein have themeanings provided below:

The terms “preferred”, “preferably”, “example” and “exemplary” refer toembodiments of the invention that may afford certain benefits, undercertain circumstances. However, other embodiments may also be preferredor exemplary, under the same or other circumstances. Furthermore, therecitation of one or more preferred or exemplary embodiments does notimply that other embodiments are not useful, and is not intended toexclude other embodiments from the scope of the present disclosure.

Directional orientations such as “above”, “below”, “top”, “bottom”, andthe like are made with reference to a layer-printing direction of a 3Dpart. In the embodiments shown below, the layer-printing direction isthe upward direction along the vertical z-axis. In these embodiments,the terms “above”, “below”, “top”, “bottom”, and the like are based onthe vertical z-axis. However, in embodiments in which the layers of 3Dparts are printed along a different axis, such as along a horizontalx-axis or y-axis, the terms “above”, “below”, “top”, “bottom”, and thelike are relative to the given axis.

The term “providing”, such as for “providing a material”, when recitedin the claims, is not intended to require any particular delivery orreceipt of the provided item. Rather, the term “providing” is merelyused to recite items that will be referred to in subsequent elements ofthe claim(s), for purposes of clarity and ease of readability.

Unless otherwise specified, temperatures referred to herein are based onatmospheric pressure (i.e. one atmosphere).

The terms “about” and “substantially” are used herein with respect tomeasurable values and ranges due to expected variations known to thoseskilled in the art (e.g., limitations and variabilities inmeasurements).

The term “near-net part” refers to a part that is printed so that it isvery close to its final shape after the initial printing. A near-netpart matches closely to the digital image provided as a source datafile, and therefore requires little or no post-print processing toachieve the desired tolerances for the size and shape for the part.

The term “out of oven” refers to a build environment that is notenclosed within a temperature controlled environmental chamber, but isused and operated outside the confines of an environmental chamber.

All cited patents and printed patent applications referenced herein areincorporated by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a multiple axis robotic build systemaccording to an embodiment of the present disclosure.

FIG. 2 is an enlarged perspective view of the system of FIG. 1.

FIG. 3 is a perspective view of a part being printed on the system ofFIG. 1.

FIG. 4 is a perspective view of the part of FIG. 3 being printed on thesystem of FIG. 1, with a tilted build platform according to anembodiment of the present disclosure.

FIG. 5 is a perspective view of a part printed with an embodiment of thepresent disclosure.

FIG. 6 is a close-up perspective view of a portion of the part of FIG.5.

FIG. 7A is a perspective view of another part printed with an embodimentof the present disclosure.

FIG. 7B is a perspective view of the part of 7A with an additionalportion printed in a planar layer-by-layer manner

FIG. 8 is a close-up perspective view of a portion of the part of FIG.7A.

FIG. 9 is section view of a part and support structure according to aprint method of the prior art.

FIG. 10 is a perspective view of an embodiment of the present disclosureprinting a part such as the part shown in FIG. 9.

FIG. 11 is a view of a series of parts showing strengths and weaknessesthereof including a part printed according to embodiments of the presentdisclosure.

FIG. 12 is an elevation view of a part and point to point supportstructures according to an embodiment of the present disclosure.

FIG. 13 is a flow chart of a method according to an embodiment of thepresent disclosure.

FIG. 14 is a flow chart of a method according to another embodiment ofthe present disclosure.

FIG. 15 is a flow chart of a method according to another embodiment ofthe present disclosure.

FIG. 16 is a flow chart of a method according to another embodiment ofthe present disclosure.

DETAILED DESCRIPTION

A system embodiment of the present disclosure uses motion of a roboticarm in six axes, and motion of a build platform in two axes, to allowprinting orientation of a fused deposition modeling part to bedetermined based on the geometry of the part, and without the need forsupporting structure. Defining print orientation based on partgeometries enables improved control over part properties, such asstrength and directionality of fiber in a composite print material, andallows printing of parts of higher quality in shorter amounts of time,and that require less post print processing.

The embodiments of the present disclosure provide for automated partproduction that change print-by-layer operations and enable truethree-dimensional printing of an extruded material to allow additivemanufacturing to be applied to near-net part structures without the needfor additional finishing steps. In some instances the parts are printedfrom a single material. In other instances, the parts are printed usingmore than one material, resulting in a composite part, which can be ofhigh commercial value. In other instances, the material composition canbe blended or varied from one end of a part build to another, fordelivery of a variety of part properties.

FIG. 1 is a perspective view of a multi-axis robotic build system 100that may be used for building three-dimensional (3D) parts. System 100includes in one embodiment a robotic arm 102 capable of movement alongsix axes. An exemplary robotic arm is an industrial robot manufacturedby KUKA Robotics of Augsburg, Germany. While six axes of motion arediscussed for the robotic arm 102 from a stationary base, it should beunderstood that additional axes or other movements are also amenable touse with the embodiments of the present disclosure, without departingtherefrom. For example, the robotic arm 102 could be mounted to move ona rail or a gantry to provide additional degrees of freedom.

The robotic arm 102 carries a print head 104, such as, by way of exampleonly and not by way of limitation, an extrusion head 104 for printingparts from a filament feed stock, powder or pellet feed stock, or thelike. In some instances, the feed stock is a polymer or copolymer whichoptionally can be loaded with secondary materials such as glass orcarbon fiber, and impact modifiers. However, the present disclosure isnot limited to the printing of parts with polymeric materials.Consumable materials that may be printed according to the presentdisclosure include, by way of example only and not by way of limitation,organic, inorganic and composite materials. Composite materials amenableto use with embodiments of the present disclosure include by way ofexample and not by way of limitation carbon fiber filled nylon, fiberreinforced thermoplastics, fiberglass reinforced thermoplastics, choppedor continuous composite fibers, and the like. The print head 104 may bean extrusion type print head, including by way of example only and notby way of limitation, a print head that utilizes a screw extruder suchas is disclosed in Bosveld et al. U.S. Pat. No. 8,955,558; aviscosity-pump liquefier such as is disclosed in U.S. Pat. No.6,004,124; a ribbon liquefier such as is disclosed in Batchelder et al.U.S. Pat. No. 8,439,665; or a gear-pump liquefier such as is disclosedin Hjelsand et al. WO 2016/014543A1. Some representative consumablematerials are disclosed in commonly-owned Batchelder et. al. U.S. Pat.No. 7,122,246; Mikulak et al. U.S. Patent Nos. 8,801,990 and 8,920,697;Bosveld et al. U.S. Pat. No. 8,955,558; and Batchelder et al. U.S. Pat.No. 8,221,669.

A build platform 106 is provided, which in one embodiment is movablealong two axes of rotation, rotation about the z-axis, and tilting(rotation) about the x-axis. Further axes of rotation may be providedwith a different build platform 106, such as but not limited to tilting(rotation) in the y-axis, and various translations. Further, differentbuild platforms with different axes of motion may also be used with theembodiments of the present disclosure without departing therefrom. Buildplatform 106 is provided in one embodiment with an extension 110 tooffer more freedom of movement of the robotic arm 102 and print head 104in the vicinity of the build platform 106. Build platform 106 could alsocomprise an additional robotic arm, also providing 6-axis movement,instead of being a fixed unit with 2-axis movement.

A controller 108 contains software and hardware for controlling themotion of the robotic arm 102 and the build platform 106, as well as theprinting operation of the print head 104.

The robotic arm 102 with extruder 104 positioned thereon is used incombination with the build platform 106 in one embodiment of thedisclosure. The eight (or more) axes of motion of the system 100 allowfor the creation and printing of parts with complex geometries thatcould not previously be printed with, for example, fused depositionmodeling systems that print in a plane, or could not be printed withoutthe use of support structures. While six axes of motion are discussedfor the robotic arm 102 from a stationary base, it should be understoodthat additional movements, such as providing a wider or longer printcapability or extended range of motion by mounting the robotic arm orbuild platform on a rail, a movable platform, or the like, are alsoamenable to use with the embodiments of the present disclosure, withoutdeparting therefrom. For example, the robotic arm 102 could be mountedto move on a rail or a gantry to provide additional range of motion.Further, different tables with different motion platforms may also beused with the embodiments of the present disclosure without departingtherefrom. Examples of such additional motion platforms include by wayof example only and not by way of limitation, trunnion tables, cradles,rail or gantry mounted motion platforms, and the like.

For printing using different materials for different portions of a partbeing built or when a new tool is required, automated tool changing maybe used. Such automated tool changing allows for additional operations,including by way of example and not by way of limitation, furtheradditive manufacturing, subtractive manufacturing, finishing,inspection, and assembly of parts. A tool change rack is schematicallyillustrated at 122 in FIG. 1, and by way of example may be configuredsuch as disclosed in Comb et al. U.S. Pat. No. 8,926,484. A tool changerack such as rack 122 may hold additional tools, extruders, subtractiveelements, or the like. Exemplary subtractive elements may includewithout limitation a radiation-emitting device, such as an excimer laserdevice as is disclosed in Batchelder U.S. Patent Publication No.20150076739. It should be understood that the tool change rack 122,while shown in one position, may be positioned elsewhere provided it isaccessible to the robotic arm, without departing from the scope of thedisclosure.

A generated tool path is utilized to control motion of the robotic arm102. However, control of the extrusion head is also used to accuratelydeposit material along the generated tool path. For example, oneembodiment of the present disclosure synchronizes timing of the motionof the robotic arm 102 with print head 104 to extrusion from the printhead 104. Embodiments of the present disclosure provide for speed up orslow down of printing, changing the extrusion rate in conjunction withrobotic movements, tip cleaning, tip changing, and other actions of theprint head 104 based on the generated tool path and motion of therobotic arm 102. As an example, extrusion from the print head 104 may besynchronized with motion of the robotic arm 102 in manners taught byComb et al. U.S. Pat. No. 6,054,077; and Comb U.S. Pat. Nos. 6,814,907,6,547,995, and 6,814,907.

For instance, when printing around a corner of a part, the speed of therobotic arm 102 and the extrusion flow rate may be decreased to provideaccurate deposition of the part. However, when printing along straighttool paths, the speed of the robotic arm 102 and the extrusion flow ratemay be increased while maintaining dimensional accuracy of the partbeing printed. Additionally, the material can be extruded in thickerbeads at faster rates in internal areas of the 3D extruded part volumethat do not affect the print quality of the part. Therefore, hollow 3Dparts, 3D parts with sparse-filled internal volumes, and or solid 3Dparts can be printed with increased speed and extrusion flow rateswithout affect the quality of the 3D part(s) being printed.Sparse-filled internal volumes include infill patterns which may beprinted in order to add desired stiffness to thin-walled structures. Aninfill pattern may be uniform throughout a part, or may be varied withinlayers or regions of a part. Two types of infill patterns are common infused deposition modeling 3D printing using planar tool paths, and canalso be utilized in printing 3D tool paths: (1) direction-parallelinfills that use short, parallel line-segments to fill the interior ofan outer part contour; and (2) contour infills that continuously offsetthe outer part contour to fill the interior. The density of material canbe altered by varying the space between these line segments, thuscreating infills that may range from being sparse, to moderate, to fullydense.

The multiple axes of motion of the robotic arm 102 and build platform106 allow for the printing of parts that are oriented not just in onesingle build plane. The use of build planes which change during printingallow the 3D parting being printed to utilize gravity for support, ifdesired. Utilizing gravity to print the 3D part reduces or eliminatesthe need for support structure to account and compensate for the effectsof gravity. This reduces the time to build a part, and reducespost-processing time of parts. The use of a robotic arm 102 and printhead 104 also allows for printing upside-down as the build substratechanges in orientation, in which the print head extrusion may opposegravity during at least portions of the build process.

Advantageously, the multiple axes of motion for the robotic arm 102 andthe build platform 106 can utilize complex tool paths for printing 3Dparts, including single continuous 3D tool paths for up to an entirepart. A single 3D tool path such as those available with the multi-axissystem 100 of the present embodiments serves to reduce issues withtraditional additive manufacturing type printing, such as stair-stepping(layer aliasing), seams, the requirement for supports, and the like.Further, without a requirement to slice a part to be built into multiplelayers all printed in the same plane, the geometry of the part may beused to determine the orientation of printing. Therefore, part strengthand consistency is improved, and build time is shortened due to a moreefficient and continuous tool path. The part can be printed with enoughaccuracy that it does not need further milling or fabrication, alsoknown as “near-net” printing. Continuous tool paths also serve toimprove consistency and accuracy of molten resin flow through theextruder because the extruder does not have to start and stop.

While some parts can be printed utilizing a single continuous 3D toolpath, the multi-axis system can also be utilized to print 3D partutilizing planar tool paths and 3D part utilizing a combination of 3Dtool paths and planar or 2D tool paths. Further, the system 100 canprint hollow parts, sparse filled parts and solid parts. When utilizinga planar or 2D build path, a seam in the perimeter of the portion of the3D part being printed can be minimized utilizing tool paths and methodsdisclosed in Hopkins et al. U.S. Pat. Nos. 8,349,239, 8,974,715 and9,724,866. The present system 100 provides the necessary capability andflexibility to print a wide variety of 3D parts with enhance extrusionflow rates, reduced build times and larger build envelopes than atypical extrusion based additive manufacturing system.

Embodiments of the present disclosure use thermal management forprinting along the tool path. In one embodiment, localized pre-heatingof the tool path ahead of the print head is utilized. The use of alocalized pre-heating operation enables elimination of a controlledthermal chamber environment or a reduction in of the temperature in thebuild environment. Localized pre-heating is performed in one embodimentwith pre-heater 120. In one embodiment, pre-heater 120 is positioned on,ahead, or near the print head 104 to provide local pre-heating of thetool path on a previously printed portion of the 3D part ahead of theprint head. In another embodiment, pre-heater 120 is positioned awayfrom the print head, in a position such as on a frame or the like, inview of the printing area. Localized pre-heating along the tool path ofthe previously printed portion of the 3D part may be performed with apre-heater using suitable pre-heating apparatus, including by way ofexample and not by limitation laser pre-heating, hot gas pre-heating,induction pre-heating, microwave pre-heating, and ultrasonicpre-heating. It should be understood that a pre-heater 120 may bepositioned elsewhere in view of the print head and tool path withoutdeparting from the scope of the disclosure, for example on a secondrobotic arm or the like. Pre-heating serves to heat the intermediatepart surface on which the new material is to be printed (such as alongthe single tool path for either a first portion or a second conformallyprinted portion on the first portion) sufficient for good adhesion ofmaterial to existing material. Part strength can be manipulated withsuch multi-layer heating treatments. Pre-heating may be performed forany portion of the part being built, including for first and secondportions thereof.

Depending upon the size of the bead being extruded and the speed of theprint head on the robotic arm 102, the amount of heat and the depth ofheat penetration into the part imparted by a pre-heater 120 can vary.For instance, when moving at a relatively fast speed with a smallerbead, then the heat is imparted into surface of the part withoutsignificant penetration into the previously printed layer. When thepenetration of the heat into the part is minimized, then the need forcooling of the just extruded material may or may not be required.However, when extruding larger beads at slower speeds, the heat tends topenetrate into the part being printed. Over time, if the heat is notremoved from the part being printed, the heat will accumulate to causethe part to become thermally unstable and deform.

Cooling quickly after deposition can be customized to remove apreviously supplied amount of heat energy (either from a hot large beadthat cannot cool quickly, or from a localized pre-heat) to a localizedarea, to return the localized regional temperature to its originaltemperature prior to the pre-heat; in essence, quickly ‘re-balancing’the local thermal energy input in order to avoid part deformation.Localized cooling can be provided in the present invention, utilizing acooling fluid including cooling gas or a cooling liquid that phasetransitions to a gas, such as but not limited to liquid nitrogen. In oneembodiment by cooling fans 130 mounted proximate the print head to moveambient air over the just printed part material. Localized cooling mayalso be employed since, in some embodiments and along some tool paths,the single tool path crosses over an area of the part 300 that has nothad sufficient time to cool on its own before another pass of the printhead over a previous part of the tool path. Localized cooling in oneembodiment is based on known tool paths and geometries, as somegeometries will be more likely to not cool sufficiently before the toolpath returns. Localized pre-heating of a previous road just prior todeposition of a new bead or road, followed by subsequent removal of thatpre-heating energy with post-cooling, in a rapid cyclic fashion, allowsfor significantly increased adhesion of layers in the z-direction, whilenot increasing part deformation.

Methods of printing include printing additional portions of a part ontop of a first existing part portion, and in some embodiments alongdifferent axes. Crossing the print axis, such as the z-axis, forexample, with a solid layer of material printed conformally to theexisting layer, provides the ability to create strong structures.

It should be understood that a controlled build environment could beused with embodiments of the present disclosure instead of anout-of-oven environment. However, local heating and cooling to providethermal management are acceptable in many printing applications. Asextrusion volume rates and manufacturing configurations become larger,controlled chamber cooling is not always feasible.

Embodiments of the present disclosure are amenable to use with compositeprinting materials. The use of composites in various industries isincreasing, as composites can provide numerous benefits over metals orother materials. Composites typically weigh less than traditional partsmade of steel or the like. In some industries, for example and not byway of limitation transportation, oil and gas, and medical, compositematerials may be used to make strong yet lightweight structures.However, previous additive manufacturing systems are constrained bylabor-intensive processes and geometric limitations.

Printing with composite materials, as is provided by the embodiments ofthe present disclosure, provide lower part weight which directlytranslates to reduced fuel consumption, reduced operating costs, and thelike. Printing of composite parts allows for customization withoutexpensive retooling, assembly consolidation, topology improvements,reduced overall part costs due to reduction in tooling expense andscrap, elimination of lifetime part buys for stocking, and the like. Theproperties of composites used in printing allow for printing withreduced amount of curl and increased strength. Should 3D printing withthe embodiments of the present invention be performed withthermo-plastics, curl compensation via temperature control may beemployed without departing from the scope of the disclosure. Curlcontrol is not discussed further herein.

Composites also provide the ability to print reinforced parts, withfiber content in the composites, such as chopped fibers, short, medium,and full length continuous fibers, incorporated into a thermoplasticmaterial, either prior to or during extrusion. With composite materials,and the provided multi-axis robotic build system 100, true near-net 3Dprinting may be achieved. Printing, for example, can be performed innearly any orientation of a print head 104, with controlled extrusionalong a single tool path. Further, printing may be configured to provideadditional strength to a part, since orientation of fibers may beconfigured for different portions of the part, or for differentsub-structures of the part.

Integration of tool paths generated by a CAD system for robotic movementare in one embodiment translated into extrusion protocols for the motionpaths that are generated. That is, once a robot motion path isgenerated, extrusion control is used to adjust print parameters toproperly print along the generated continuous tool path. Such parametersinclude by way of example only and not by way of limitation, printspeed, extrusion rate, and the like.

FIG. 2 is a close-up view of a portion of system 100 showing axis map200 with arrows 202 and 204 representing rotation of the build platform106 about the z- and x-axes, respectively. The use of the multiple axisrobotic arm 102 and the multiple axis build platform 106 allow fororientation of a part being printed to rely on gravity in lieu of atleast some printed support material. Specifically, a part being printedcan, with the multiple axis build platform 106, be oriented so thatfeatures of the part being printed are printed to reduce the likelihoodof sagging or failure due to lack of support. When an air flow source isdirected toward the newly deposited tool path region, the part will coolmore quickly and also enable quicker fabrication of complex shapes.Examples of parts printed with a system such as system 100 are describedbelow and include, but are not limited to hollow parts printed with oneor more continuous three-dimensional tool path, a part printed with aportion printed 3D tool path another portion printed with planar toolpath. The illustrated 3D parts are exemplary and non-limiting in naturewhere the present system 100 can print solid parts, hollow parts, sparsefilled parts and combinations thereof. Some thermoplastic near-net partsthat would require support in a typical fused deposition modeling-typeprinting system may not even need orientation to account for gravity,but may be printed directly with motion of the robotic arm 102 withouttilting of the build platform 106.

FIG. 3 shows a multi-axis robotic build system 100 in process ofbuilding a part 300. Part 300 is, in this embodiment, built on the buildplatform 106, extended portion 110, and a build sheet 310. The buildsheet 310 is removably adhered to the build platform 106, such as by wayof example adherence by vacuum force as is disclosed in Comb et al.,U.S. Pat. No. 5,939,008. The build sheet 310 provides a removablesubstrate on which to build the part 300. Other print foundations areknown and may be used in place of the sheet substrate, for example, abuild substrate, which may be a tray substrate as disclosed in Dunn etal., U.S. Pat. No. 7,127,309, fabricated from plastic, corrugatedcardboard, or other suitable material, and may also include a flexiblepolymeric film or liner, painter's tape, polyimide tape, or otherdisposable fabrication for adhering extruded material onto the buildplatform 106.

Part 300 is printed in one embodiment with a continuous 3D tool path.That is, a portion or entirety of part 300 may be printed using a singletool path, not a series of sliced layers. For example, printing may bein a helical pattern, with gradually increasing height, yet printed witha single continuous extrusion of material from print head 104. Forexample, to print part 300, the robotic arm 102 could move and the buildplatform 106 could be stationary. However, the build platform 106 couldrotate x-y plane, gradually increasing in z.

It will be understood that combinations of motion of the robotic arm 102and build platform 106 may be made to provide for the printing of partsor parts in changing build orientations, including parts that wouldnormally use support structures, without the use of support structures.It is also understood changes in extrusion rates can be synchronizedwith either movement of the robotic arm 102 or the build platform 106 orboth the robotic arm 102 and the build platform 106 based upon the partgeometry to accurately print the parts near net.

The ability to orient a part being printed in a specific chosenorientation, via motion along multiple axes of the build platform 106,as well as the axes of motion for the robotic arm 102, provideembodiments of the present disclosure that allow printing of a partalong multiple axes, including axes that are oriented in differentdirections, such as but not limited to normal to each other. Suchdifferent axes, along with the use of composite materials such as thosecontaining continuous fibers or known fiber orientations, allows for theprinting of parts that have higher continuity with improved strength.That is, in embodiments of the present disclosure, a first portion of apart may be printed with an orientation of printed material along oneaxis, for example the x-axis, and a second portion of the same part maybe printed with an orientation of printed material along a second axis,for example the z-axis. Still further, embodiments of the presentdisclosure provide the ability to conformally print layers of materialon already laid down material, along a different axis.

FIG. 4 shows further printing of part 300, after printing of a firstportion 302 thereof, comprising in this embodiment a dome shapedportion. Portion 302 is formed in this embodiment with a single 3D toolpath printing operation. An end 306 of the tool path over which portion302 is printed is shown in FIG. 5. Following printing of the firstportion 302 of part 300, the build platform 106 is rotated about thex-axis to allow for the printing of a second portion 304 of the part300. Second portion 304 is in one embodiment a series of ribs with theirprinting direction substantially perpendicular to the printing directionof the first portion 302 (see FIGS. 5 and 6 for additional views of part300). The embodiments of the present disclosure allow for this type ofprinting of a first portion of a part along one axis, followed byconformal printing of a second portion of the part along a second,different axis, than the first portion 302. Conformal printing ofportion 304 to portion 302 is along portion contact edge 308. Contactedge 308 is the edge along which portion 304 is initially conformallyprinted to portion 302.

One skilled in the art would understand that a second portion of a partadded upon a previously built portion of the part would generally differin temperature, and thus, also have challenges with respect toadherence. Temperature control of the build space would generally beused as described herein to allow for strong adherence between the twoportions. Through the use of a localized pre-heating source (e.g.,pre-heater 120) prior to deposition of material of the second tool pathportion 304 being printed on the first portion 302, pre-heating orannealing of the surface along the tool path for the second portion 304is performed. One of skill in the art would recognize that while someranges of time and/or distance from pre-heating to printing aredescribed herein, that different materials will have differenttemperatures and heating and cooling rates, that determination of timeranges is material dependent, and that such determination is within thescope of the disclosure and the skill of one of skill in the art.

FIGS. 5-8 show representative parts printed using apparatus and methodembodiments of the present disclosure.

FIGS. 5 and 6 show further details of part 300. The tool path for firstportion 302 is in one embodiment a single tool path. The tool path forthe second portion 304 is in one embodiment a single 3D tool path. In asingle 3D tool path printing operation for a portion of the part,typically comprising a portion that would be required to be printed inmultiple sliced layers in an additive manufacturing system, the entireportion is printed in a single path. In the part 300, for example,portion 302 is printed with a single 3D tool path in a general axisindicated by arrow 320. Then, following printing of portion 302, portion304 is printed conformally to portion 302 in a different single toolpath printing operation. Portion 304 is printed in a general axisindicated by arrow 330. However, it should be noted that certain partsof the portions may be printed along the same axis. The nature of true3D printing allows such printing, since the six axes of motion of therobot, supplemented by additional motion of the robot or build platformto expand the range of motion, allow for printing in differentdirections relative to earlier extruded material, including the printingof conformal portions of a part onto existing portions of the part.

Referring to FIGS. 7A and 8, part 700A is printed in a similar fashionas part 300, with first portion 702 being printed first using a single3D tool path in a helix, printed using the robotic arm 102, print head104, and build platform 106, with the part 700A oriented with respect tothe axis map 710. Following completion of printing of first portion 702,second portion 704 is printed on first portion 702, conformallytherewith beginning at contact edge 708. Second portion 704 of part 700Ais printed in one embodiment with part 700A tilted along the x-axis,with the print head 104 printing a single tool path in a helix along therotated z-axis (e.g., rotation about the x-axis to align the z_(rotated)axis 90 degrees about the x-axis from the z_(original) axis as shown inaxis map 810) while the part 700A is rotated about the original z-axis.When an apparent end 706 of the path is reached, the print head 104 isindexed in the original x-axis (now the z-axis) without requiringre-registration of the print head, and printing on the single tool pathcontinues back over the just printed part of the portion 704. In thisway, the apparent end 706 is not an end of the tool path, but is simplya part of the tool path while printing continues.

Referring to FIG. 7B, the part 700B is printed in a similar manner asdescribed with respect to the part 700A where the first portion 702 andthe second portion 704 are constructed utilizing continuous 3D toolpaths. The part 700B includes a substantially solid base constructed ofa plurality of planar layers 712. Each layer includes a boundary 714extruded about a perimeter of the base and a substantially solidinterior region that is filled utilizing a raster tool path 716. A seamin the boundary 714 of the portion of the 3D part being printed can beminimized utilizing tool paths and methods disclosed in Hopkins et al.U.S. Pat. Nos. 8,349,239, 8,974,715 and 9,724,866.

FIG. 7B illustrates that the system 100 can be utilized to printportions of parts with continuous 3D tool paths, planar tool paths andcombinations thereof. The parts or portions of the parts can be hollow,sparse filled and/or solid depending upon the geometry and features ofthe part being printed.

A method of printing a part according to an embodiment of the presentdisclosure includes printing a part along a single tool path using arobotic arm capable of moving in six axes on a build platform capable ofmoving in at least two axes, with controlled extrusion along the singletool path and localized pre-heating of the tool path prior to printing.Printing a second portion of the part is performed conformally on afirst portion of the part, including printing in a second axis differentthan the first axis. What is meant by printing conformally is that atleast the first layer of the second portion conforms to a surface of thefirst portion.

Methods of the present disclosure include aligned direction of buildingof a portion of the part followed by aligned direction of buildinganother portion of the part along a different axis, with controlledextrusion depending upon tool path, tool speed, and pattern.

Printing according to an embodiment includes analysis of the geometry ofthe part to be built, choosing the axis of printing based on theanalysis of the geometry to build along a single tool path or multipletool paths. In so doing, the orientation of the part during printing iscontrolled to rely on gravity so that supports which are typically usedin printing parts are not necessary.

With embodiments of the present disclosure, printing may be performedwith the print head 104 in any orientation, including upside down. Thisallows for the geometry of the part to be used to determine theorientation of the build platform with respect to the print head duringprinting. During a build, it may be advantageous to use a cooling fluidsuch as ambient or cooled air (or other gas) flow or a cooling liquidthat transforms to a gas at process temperatures, such as liquidnitrogen, to be directed at the recently extruded material, such as bycooling with fans 130 as described above. Higher airflow or other forcedgases may enable quicker solidification of shapes which would normallyoppose gravity during the build. Utilizing a cooling fluid also allowsfor higher extrusion rates because the part being printed is maintainedat a thermally stable temperature.

Utilizing pre-heating along the tool path, followed by extrusion of thematerial imparts heat into the part in a localized region. The coolingfluid can be used to remove the heat from the local region to thermallymanage the printing of the part.

Printing with a print head 104 in any orientation allows for geometry ofa part that is being printed to determine the print path. That is, atraditional layer by layer printing using multiple sliced layers forprinting a part can lead to situations in which the part requires asignificant amount of support, or in which the layer by layer approachresults in a part that fails to have a structural form that issufficient for its purposes. Further, complex parts can be verydifficult to print in a traditional layer by layer printing process, dueto the inability of support structures to provide proper support, or forthe finished part to meet quality standards.

For example, near-net parts of more complex shape, such as part 900shown in cross-section in FIG. 9, are very time consuming, and supportdependent, when printed using traditional layer by layer methods. In alayer by layer method of printing part 900, which is an elongatedtubular member, such as a muffler pipe or other curved hollow pipe, alayer by layer printing method would slice the part into a number oflayers indicated at layer lines 902. For each layer, starting at abottom 904 of the part, the portion of the actual part 900 is indicatedat section 906. Support structures for later portions of the part atlater layer heights must also be deposited. Support structure is showncross-hatched at sections 908 of the first layer at bottom 904. Supportstructures 908 are used to support portions of the part 900 that will beprinted later in the layer by layer printing process, such as sections910, 912, and 914. Support structure is typically printed usingdifferent material, so the first layer at bottom 904 of part 900 will beprinted with part material for section 906, and with support materialfor sections 908.

Changing between part material and support material is typicallyaccomplished by swapping of the print head, which involves one or moreof moving the print head away from the part, swapping the print headitself, purging material from the new print head, and registering thenew print head to the part, before printing of support material canbegin. With each layer, at least one swapping of print head, with allthe attendant operations, is performed. For nearly every layer of part900, it can be seen that both part material and support material wouldneed to be printed. This increases the print time, material cost, andpost-processing time and expense. Further, at layers indicatedespecially at 910 and 912, the print layers do not follow the contoursof the part 900 that would make the most sense in printing. That is, atportions 910 and 912, the layers of part material are substantiallyparallel to the longitudinal axis of the part 900 at that portion. Thiscan lead to issues with stair-stepping (layer aliasing) at the partedge, as well as reduce the overall strength and quality of the part900.

A part such as part 900 which when sliced for additive manufacturing isdifficult to properly produce in a near-net fashion with planar toolpaths, for example having problems with stair-stepping (layer aliasing)and strength, can be printed with embodiments of the present disclosure,for example, using the 3D continuous tool path, to have consistentstrength throughout. FIG. 10 shows an embodiment of printing part 900using system 100. Embodiments of the present disclosure allow for theprinting of the same part 900 with no support structure, as is shown inFIG. 10. Further, the single 3D tool path enabled by the embodiments ofthe present disclosure allows for the building of the part 900 withconsistent longitudinal strength, since the helical tool path of theprint head can consistently align with the structurally soundorientation of the material deposition. In FIG. 10, the multiple axisrobotic build system 100 prints the part 900 starting at its bottom, andusing a single helical tool path that traces the exterior of the part900 and aligns along the longitudinal axis of the tubular part. As isseen in FIG. 10, the area 912 is being printed, with a tool path for theprint head 104 that reduces or eliminates stair-stepping (layeraliasing) and supports, thereby printing the part 900 more quickly,using less material, and along its geometry so as to make the part 900consistent and strong. Embodiments of the present disclosure may be usedto vary strength of parts being printed, using alignment and orientationof fibers in print material, as well as with composition of layers,including extrusion on existing parts and at different orientations,providing even and consistent strength for most geometries, orspecifically varying the strength or flexibility within portions of apart by varying build pattern, density or composition.

Another representative part that is easily built with embodiments of thepresent disclosure is a part having, for example, an internal latticestructure normal to a surface of the part. Embodiments of the presentdisclosure allow for printing of such a part, using the eight axes ofmotion between the robotic arm and build platform. Examples of partsthat may be printed using method and apparatus embodiments of thepresent disclosure that are not amenable to printing with standard fuseddeposition modeling techniques and machines include wing tips of anairplane wing, such as parts that curve upward at their end, and whichneed to be structurally strong, often including a honeycomb latticewithin the inner structure of the wing, with the lattice structure beingspecifically aligned in a proper orientation to the inner portion of thewing.

FIG. 11 illustrates limitations of current layer-by-layer fuseddeposition modeling print techniques. Part 1110 illustrates a part withstress and strength requirements around stress points and break points.A metal part provides strength and stress performance suitable for use,as shown at part 1120. A composite laminate part 1130 also passes stressand strength tests. Parts 1140 and 1150, printed with layer by layerextrusion processes, in which layers are printed along arrow 1142 inpart 1140 and along arrow 1152 in part 1150, fail one of the stress orstrength tests and pass the other test. The layer by layer print modelof current fused deposition modeling printing systems is limited to asingular build plane and does not allow optimization of the part qualityor build process by printing along multiple axes or multiple buildplanes. However, a part 1160 printed using the embodiments of thepresent disclosure, along multiple axes with a tool path that travels inall directions as indicated by arrow 1162, provides a completed partthat can pass strength and stress tests dues to the ability of theembodiments of the present disclosure to align composites and printorientations to provide strength and stress parameters that meetrequirements.

Printing in multiple degrees of freedom, with or without localizedcooling, also allows for the use of narrow, point to point supportstructures. For example, FIG. 12 shows support structures tacked betweena part 1200 and a support surface 1210 (1202) and between separate spotson a part (1204), respectively. Thin support structures such as 1202 and1204 are not possible in a layer by layer printing operation. Such thinsupport structures are rapidly printable, and do not use as muchmaterial as traditional support structures. Interpart structures such as1204 may be used, for example, could be used to reduce compression orsagging of portions of a part without using a full traditional supportstructure built from the build plane up.

Embodiments of the present disclosure are amenable to printing outsideof an oven or other heated enclosure. The embodiment of FIG. 1 is shownin an out-of-oven environment. In a printing environment not confined toan oven, such as printing out-of-oven, the equilibrium temperature of anunfinished part is roughly equivalent to the temperature of theenvironment. This, unlike in-oven printing, can significantly reduce thewindow in which adhesion of new material to previously printed material,as well as other build properties, can be achieved.

However, print techniques such as localized heating of previouslyprinted portions of the part along a tool path, followed by extrusion ofmaterial along the tool path to increase bonding between the layers ofmaterial can be utilized in heated build environments, including buildchambers. Additionally, localized cooling of the recently extrudedmaterial along the tool path can be utilized to maintain the thermalstability of the part being printed.

Embodiments of the present disclosure use pre-heating of portions of apart, for example using a laser system, a gas jet system, or acombination of laser and gas jet systems. Referring back to FIG. 1, theheater 120 may, in an alternative, be a pre-heating gas jet, laserheater, or combination thereof as discussed herein. Using pre-heating,the build properties and adhesion desired for part printing may beenhanced. Such enhancements enable the building out-of-oven of partssimilar to or better than in-oven build quality. Further, suchenhancements enable new families of material for use in part buildingout of oven.

When pre-heating is accomplished using a laser pre-heater, heatingenergy is applied to a small area of previously printed layer,immediately before, or substantially immediately before, the depositionof a new bead of material. In one embodiment, this pre-heats a coolerside of the interface shared between the new layer and previous layers,and improves adhesion between the new layer and the previous layer. Thispre-heating also enables the use of high temperature materials thatwould not otherwise adhere to themselves well or at all in an out ofoven environment.

An array of laser elements may be used in one embodiment. In embodimentsof the present disclosure in which a precomputed and known tool path andlayer plane shape is used, such an array of laser elements may be usedinstead of a single laser source. In such a configuration, individualelements of the full laser array can be engaged to apply laser heatingonly where needed. This prevents overheating adjacent tool paths,especially in tightly packed raster patterns where a print head rapidlyreturns to nearly the same spot on the part within a span of time thattypically does not allow for full cooling. Furthermore, by varying laserpower, the amount of adhesion gained from pre-heating can be controlled.As laser energy is not bounded by a specific maximum temperature, laserpre-heating is limited only by a maximum temperature that the polymercompound used for printing can reach before degradation occurs.

When pre-heating is accomplished using a gas jet, a focused, high speed,high temperature flow of air directs heat onto a deposition path, forexample, just ahead of a print head. Similar energy input to a lasersystem can be gained. However, maximum temperature may be limited. Thatis, hot gas can be introduced at a specific temperature, and there is norisk of the part temperature exceeding the temperature of the gas. Thechoice of gas in one embodiment is an inert gas. Air could be used, orother gases, depending upon a desired temperature for the pre-heating.By using a gas other than air, in one embodiment an inert gas, highertemperatures could be achieved than in a locally air based environmentdue to the reduced likelihood of polymer degradation in an inertenvironment.

Further, depending on design and capability of a gas jet pre-heater,such a jet could also be used, with a different gas or the same gas at adifferent temperature, to provide cooling, pre- or post-printing. Anarray of gas jets may also be provided, allowing for directionallycontrolled heating and cooling simultaneously. By applying forcedconvection with a gas jet or gas jet array using room temperature orcolder air/gas, a material bead may be rapidly cooled immediately beforeor after extrusion. Other fluids can also be utilized to cool thepreviously deposited material, including, but not limited to, liquidnitrogen. Post-cooling enables, for example, large bead diameterextrusion to be utilized with short return times, such as a rasterpattern to reduce the time required to print parts; increased bridgingdistances; tailored adhesion, especially when combined with pre-heating;and control of material morphology. Pre-cooling enables, for example,creation of weak points or failure points in a part at specific spotswithin the part, for example by reducing adhesion.

Bead precooling in one embodiment allows a part to be printed with thecapability to purposefully disrupt the development of adhesion inspecific spots within the part. This may be used, for example, tointroduce intentionally weakly adhered zones into the part itself, suchas would be necessary to mitigate failure by channeling energy to aspecific failure site instead of another more critical area of theobject. Also, it may be used to target a localized region for break-out,such as a future hole, after build. Further, this may be used, forexample, to reduce adhesion between the object and another build of amodel to be used as support. In some configurations, a model materialwill sufficiently adhere to previously printed material. However, byintentionally cooling one surface of a part prior to deposition, theshared interface will not achieve the best temperatures for goodadhesion. This allows the formation of tailored adhesion at these modelto model as support interfaces.

Localized pre-heating of a portion of a part, or a portion of a toolpath, prior to deposition, allows for the use of multiple differentmaterials in a 3D printing operation. By pre-heating small depths ofmaterial over small times in an out of oven environment, instead ofkeeping the complete object at an elevated temperature in an oven,multiple materials can be printed together. This is enabled in oneembodiment by the local pre-heating of one of the two materials to thecompatible temperature range of the second of the two materials,enabling adhesion to develop in an otherwise unusable temperature rangesuch as the temperature used when printing in oven. Switching from onethermoplastic material to another in the same part typically has notbeen feasible in a controlled temperature oven environment, because eachmaterial requires a particular build temperature range associated withits material melt characteristics. By utilizing localized buildtemperature control through pre-heating and/or precooling, switches inmaterial deposition can be made mid-build. By way of example only andnot by way of limitation, local pre-heating in an out of oven embodimentwould also allow for the printing of an elastomer on a structuralmaterial, both of which sufficiently adhere in different temperatureranges. Because the temperature is raised locally, the temperaturecontrol can be done over a short time period, so that part stability ismaintained.

In one embodiment, additives are added to the print material to alterthe acceptance of energy sources. Additives, by way of example only andnot by way of limitation, include carbon black and/or dyes. Additivesare used in one embodiment to create print materials that perform incertain ways under certain conditions. The use of additives furthereases the use of different materials in the same part. This materialtuning allows certain wavelengths of laser energy, for example, to havedifferent effects on different materials. For example, when a lasersource emits energy at a wavelength that a target print material absorbsenergy, the material may respond differently that base material withoutadditives.

In one embodiment, an emitting wavelength of a laser pre-heating sourceis known, and, through use of additives, a material to be printed ismodified, such as with the use of additives, to create a material with adifferent range of acceptance or rejection of heating energy sources.Such modifications tune the material to absorb or reject energy, forexample, at a particular wavelength or range of wavelengths. Tuning tovisible wavelengths, infrared wavelengths, ultraviolet wavelengths, andthe like can be performed with the use of additives. Responses ofmaterials to various wavelength energy depends upon a variety ofphysical and chemical characteristics, for example. Different materialsalso have different responses to different additives, and can allow forfurther tuning. Additives may be employed to, for example, controlabsorptivity, control conductivity, control specific heat capacity, andthe like, of print material. Tuning of materials therefore allowsmaterials that have different melting and adhesion temperatures to bejoined in an out of oven configuration, with the assistance of localpre-heating and precooling.

Further embodiments use local pre-heating and/or precooling to determinepart characteristics of a part or a portion thereof. For example,depending on part structure, minimum return time, print bead size, andthe like, pre-heating and/or pre-cooling can make residual stresslocalized. For example, pre-stress points may be built in, or pre/postheating and cooling can be used to reduce residual stress by tuningtemperature profile of beads, for example, to elongate cooling time fora small bead, and/or decrease cooling time for a large bead. In ovenbuilds cannot accomplish this.

While pre- and post-heaters and pre- and post-coolers are shown in closeproximity to the print head in some embodiments, it should be understoodthat the placement of pre- and post-heaters and pre- and post-coolersmay be modified within the scope of the present disclosure.

Minimum return time is the time between the deposition of a bead at apoint on one layer and the deposition of a bead at the same point on thenext layer. During a part build, heat is transferred out of depositedbeads by conduction and convection into the previous layers andenvironment, respectively. For small bead diameters and sufficientlylarge parts, heat from newly deposited beads is sufficiently transferredaway by the time new material is deposited atop.

Minimum return time becomes a factor for small features and for near-netpart creation, as well as increased manufacturing extrusion rates, whereresin does not have time to transfer sufficient energy into itssurroundings before the next layer is deposited, and for large beadsizes. In fact, for sufficiently small features or large bead sizes,temperature runaway within a part is possible. In this case, temperaturein the previous layers increases over repeated depositions. This resultsin increasingly slow cooling of the newest layer and potential mobilityof previous layers, which should remain effectively locked into shapeafter their own deposition. In some printers, return time isartificially lengthened to ensure that a previously deposited layer issufficiently below a critical temperature before deposition of a newlayer.

However, this may not be feasible for large beads which carry muchgreater thermal mass than smaller beads. For very large bead diameters,regardless of feature size, minimum return time lengthens from tens ofsecond to many minutes, dramatically increasing the total build time,especially for small to moderately sized features. Not only do theselarge diameter beads require long cooling times, but they may alsoremain mobile long enough that they will distort and sag under their ownweight before solidifying, again leading to failure. Rapid cooling oflarge diameter beads allows for their use, widening the range of beadand feature size.

Embodiments of the present disclosure counter a buildup of heat withrapid localized cooling. By rapidly removing heat (in one embodiment aspecific amount of heat) shortly after deposition, the minimum returntime is reduced, allowing both rapid building of small features and theuse of large diameter beads, ultimately reducing build time whilereducing potential part failure or non-failure distortions. In oneembodiment, the amount of heat removed is sufficient to cool the partagainst deformation, but not so much as to prevent adhesion.

In the presence of localized cooling, localized heating is also used inone embodiment. As localized heating promotes adhesion, localizedcooling inhibits it. Thus, local pre-heating prior to deposition allowsincreased adhesion, and localized rapid cooling locks bead shape andreduces minimum return times.

Post cooling with a gas jet, as opposed to a fan blowing ambient air,allows for greater bridging distances of unsupported or underneath beadregions than in-oven print environments. Using more effective gas jetcooling, beads may be solidified more quickly, further extending thebridging distance. For bridging, pre-heating of an upcoming junction isapplied in order to maintain sufficient adhesion at the bridge unionsite. The capability to rapidly cool large diameter beads which have alarger thermal mass and thus cool more slowly than thinner beads allowsfor reduction of minimum return time, and increased part integrity. Thisenables lower usage and build times for current support structures, aswell as new types of support structures, such as tack supports asdescribed herein.

For semi-crystalline polymers, or for alloys incorporatingsemi-crystalline polymers, relative crystallinity is a function of thetemperature and temperature rate of change. Generally, a slower coolingprocess yields more relative crystallinity than a more rapid coolingprocess. One post-cooling embodiment rapidly drives a recently extrudedmaterial through its crystallization range, leaving it relativelyamorphous as compared to a material which cooled more slowly.Conversely, post-heating using, for example, a pre-heater such as alaser pre-heater, gas jet pre-heater, or combination thereof, thematerial could be kept at a higher temperature for longer, enabling theformation of more crystallites.

FIG. 13 is a flow chart of a method 1300 of printing a 3D part with anadditive manufacturing system. Method 1300 comprises printing a firstportion of the part along a first 3D tool path in block 1302. A secondportion of the part is printed conformally to a surface of the firstportion of the part along a second 3D tool path in block 1304.

FIG. 14 is a flow chart of another method 1400 of printing a 3D partwith a multiple axis robotic build system. Method 1400 comprisesprinting the part along a 3D tool path with an extruder mounted on arobotic arm that moves in six degrees of freedom in block 1402. The partis oriented during printing based on geometry of the part being printedseparate from the movement of the robotic arm in block 1404.

FIG. 15 is a flow chart of a method 1500 of out of oven printing of a 3Dpart. Method 1500 comprises providing an extruder on a robotic armhaving six degrees of freedom in block 1502, and providing a build planemovable in two axes of rotation in block 1504. A first portion of thepart is extruded along a first three-dimensional tool path in block1506. A second portion of the part is extruded conformally to a surfaceof the first portion of the part along a second 3D tool path in block1508. Extruding a second portion of the part comprises locallypre-heating a portion of the second 3D tool path of the second portionof the part prior to extruding on that portion of the tool path.

FIG. 16 is a flow chart of another method 1600 of printing a 3D part.Method 1600 comprises extruding a portion of the 3D part in block 1602,and pre-heating the portion of the tool path along which a next layer ofthe 3D part is to be printed in block 1604. Additional part material isextruded along the pre-heated tool path to increase adhesion between thenewly extruded material and the previously extruded material in block1606

While embodiments of the present disclosure are described with respectto a multi-axis printing system, it should be understood thatembodiments of the present disclosure may also be used with bothadditive and subtractive manufacturing processes. Embodiments of theapparatus and methods of the present disclosure provide a true 3Dprinting process using a combination of robots with positioners,cradles, gantries, and the like, to align the printing process withgeometries of the part to be printed, along a single tool path ormultiple single tool paths including printing of portions of the partconformally onto existing previously printed portions of the part.

1-29. (canceled)
 30. A multiple axis robotic additive manufacturingsystem, comprising: a movable robotic arm; a build platform movable inat least two degrees of freedom and independent of the movement of therobotic arm to position a part being built to counteract effects ofgravity based upon part geometry; an extruder mounted at an end of therobotic arm, and configured to extrude material with a plurality of flowrates, wherein movement of the robotic arm and the build platform aresynchronized with the flow rate of the extruded material to print thepart using 3D tool paths; and a pre-heater configured to locallypre-heat a previously printed portion of the part along a 3D tool pathprior to extrusion of material along the 3D tool path by the extruder toconformally print a subsequent portion of the part.
 31. The multipleaxis robotic additive manufacturing system of claim 30, wherein thebuild platform is configured to rotate about a central axis.
 32. Themultiple axis robotic additive manufacturing system of claim 30, whereinthe build platform is configured to tilt in a plane from substantiallyvertical to substantially horizontal.
 33. The multiple axis roboticadditive manufacturing system of claim 30, wherein the build platform isconfigured to rotate about a central axis and to tilt in a plane fromsubstantially vertical to substantially horizontal.
 34. The multipleaxis robotic additive manufacturing system of claim 30, wherein therobotic arm is movable in six degrees of freedom.
 35. The multiple axisrobotic additive manufacturing system of claim 30, wherein thepre-heater comprises a gas jet heater, a laser source heater or a hybridgas jet and laser pre-heater.
 36. The multiple axis robotic additivemanufacturing system of claim 30, and further comprising a coolerconfigured to actively cool a portion of the part along the 3D tool pathafter extrusion of the material.
 37. The multiple axis robotic additivemanufacturing system of claim 36, wherein the cooler is a gas jetcooler.
 38. The multiple axis robotic additive manufacturing system ofclaim 30, and further comprising: a tool changer configured to changethe extruder for another tool.
 39. The multiple axis robotic additivemanufacturing system of claim 38, wherein the tool changer is configuredto change the extruder for a subtractive manufacturing tool.
 40. Amethod of printing a 3D part with a multiple axis robotic build systemcomprising: printing a first portion of the part on a build platform byextruding thermoplastic material along a single continuous first 3D toolpath with an extruder mounted on a movable robotic arm; orienting thepart by moving the build platform during printing based on a geometry ofthe part being printed separate from the movement of the robotic armwherein the movement of the build platform and the movement of therobotic arm are synchronized to print the part without supportstructures; and locally pre-heating previously extruded thermoplasticmaterial on a surface of the first portion of the part along a second 3Dtool path, wherein locally pre-heating comprises pre-heating toapproximately a temperature at which thermoplastic material to beextruded for printing a second portion of the part will adhere to thepreviously extruded thermoplastic material; and conformally printing thesecond portion of the part by extruding thermoplastic material along thesecond 3D tool path, wherein the second portion of the part hasincreased adhesion to the first portion of the part due to thepre-heating.
 41. The method of claim 40, wherein the method comprisesprinting a net or near-net part.
 42. The method of claim 40, and furthercomprising changing a rate of extrusion of the extruder based on partgeometry, a speed of the robot arm, a speed of the build platform orcombinations thereof.
 43. The method of claim 40, wherein the secondportion of the part is printed from a different thermoplastic materialthan is used to print the first portion of the part.
 44. The method ofclaim 40, wherein the single continuous first 3D tool path is a helicaltool path.
 45. The method of claim 40, wherein the single continuousfirst 3D tool path is a helical tool path and wherein the first portionof the part is a tubular member or a dome-shaped member.
 46. The methodof claim 40, wherein the first portion of the part is a tubular memberor a dome-shaped member and the second portion of the part comprises afin, and wherein the second 3D tool path forms a contact edge of thesecond portion of the part.
 47. The method of claim 40, and furthercomprising printing a third portion of the part along planar tool paths.48. The method of claim 40, wherein the robotic arm moves in six degreesof freedom.
 49. A method of out of oven 3D printing of a part,comprising: providing an extruder on a movable robotic arm; providing abuild platform; extruding a first portion of the part along a first 3Dtool path; and extruding a contact edge of a second portion of the partconformally to a surface of the first portion of the part along a second3D tool path; wherein extruding a contact edge of a second portion ofthe part comprises locally pre-heating a portion of the first portion ofthe part along the second 3D tool path prior to extruding on thatportion of the first portion of the part.
 50. The method of claim 49,and further comprising actively cooling the extruded material along thepreviously pre-heated second tool path.
 51. The method of claim 49,wherein the material of the first portion is different from the materialof the second portion.
 52. The method of claim 49, wherein the roboticarm moves in six degrees of freedom.